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DiscoverCircuits.com -- Hobby Corner
Last Updated on:
Friday, September 20, 2013 05:49 PM
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Constant Current /
Current Sink
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1 Amp Current Injector Circuit
designed by David A. Johnson |
| I designed and built this thing many
years ago. I published the hobby circuit in the now defunct “Radio Elecronics”
magazine back in 1992. The electronic circuit injects a precise 1 amp of current
into any unknown resistor, up to about two ohms. Two alkaline C cells power the
complete circuit. |
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voltage booster provides the current control circuit with a higher voltage, to insure
the electronic circuit operates properly, even as the battery voltage drops. A
single LED provides both power monitoring and a low battery indicator. The current
source is activated when a pushbutton switch is pressed. |
| With a good digital
voltmeter, you can use this device to measure resistances down to less than one
micro ohm. That is 0.000001 ohms. I often use it to measure contact resistance of a
relay or the resistance of big chunk of heavy gauge wire or the resistance of a
copper trace on a circuit board. You can also use it to measure the voltage drop of
a power diode, when conducting one amp of current. For more details on this
circuit, click here. |
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Click on Drawing Below to view PDF version of
Schematic |
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Constant Current /
Current Sink
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eMail David A.
Johnson, P.E. about this circuit |
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